From 967c05aee439e6e5d7d805e195b3a20ef5c433d6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 8 Jun 2019 10:22:49 -0700 Subject: [PATCH] tcp: enforce tcp_min_snd_mss in tcp_mtu_probing() If mtu probing is enabled tcp_mtu_probing() could very well end up with a too small MSS. Use the new sysctl tcp_min_snd_mss to make sure MSS search is performed in an acceptable range. CVE-2019-11479 -- tcp mss hardcoded to 48 Signed-off-by: Eric Dumazet Reported-by: Jonathan Lemon Cc: Jonathan Looney Acked-by: Neal Cardwell Cc: Yuchung Cheng Cc: Tyler Hicks Cc: Bruce Curtis Signed-off-by: David S. Miller --- net/ipv4/tcp_timer.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 5bad937..c801cd3 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -155,6 +155,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; mss = min(net->ipv4.sysctl_tcp_base_mss, mss); mss = max(mss, 68 - tcp_sk(sk)->tcp_header_len); + mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss); icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); } tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); -- 2.7.4